Irony: Record Daily Steelhead Counts At Bonneville Dam Due To Heat Wave

The old daily record at the giant Dam on the Columbia River near Portland, Oregon was around, 14,000 steelhead trout. So what is the new peak of 34,000 fish in a single day all about? It seems that the fish were hiding in cooler downstream tributaries waiting for a break in the hot weather before climbing to their spawning grounds.

Because that was a full 10,000 more than the day before, Hymer figured someone must have inadvertently punched in an extra digit on the calculator. He had good reason to believe so. In the 71 years since fish counting began at Bonneville, the previous record for the daily steelhead count amounted to 14,432. Then came Wednesday’s count: 28,314. On Thursday, the number spiked at 34,054.

The incredible steelhead counts weren’t typos. At the dam, fish counters recorded as many as 1,700 silvery flashes zipping past in a single hour on Thursday a rate that equates to a new fish every couple of seconds. … Biologists attribute this week’s bulging daily counts at Bonneville largely to the searing heat wave two weeks ago. Several days of triple-digit heat warmed the river to as high as 75 degrees at Bonneville, well above the comfort level for cold-water fish.

‘When you get up to 74, 75 degrees, fish just don’t move,’ Hymer said. ‘In sport fisheries below Bonneville, we saw steelhead duck into tributaries like the Cowlitz, Lewis, even to some degree the Kalama. Fish are trying to cool off as much as possible.'” See full article.